Transcriptomic Changes in Broiler Chicken Hypothalamus Following Chronic Heat Stress

Abstract

Chronic heat stress induces severely detrimental effects on bird health by interfering with numerous aspects of a bird’s health. One of the primary homeostasis-defending organs of the body is surprisingly small given its integrative capacity and ability to effect multi-system, dramatic downstream changes: the hypothalamus. RNA-Seq was used to identify the differentially expressed genes (DEG) in the Chronic Heat Stress (CHS) group compared to the Control. Ingenuity Pathway Analysis was performed on the DEG and used the identifiable DEG to generate the most likely ontological pathways affected during CHS. The top up and downregulated genes were then validated using quantitative Real-Time PCR (qPCR). RNA-Seq identified “Nervous System Development and Function” as a top affected pathway, and three significantly downregulated proteins (p ≤ 0.05, Fold Change ≤ -1.5) stood out: DCX, GAN, and SPECC1L, all of which have been implicated in some aspect of cytoskeletal development or organization within the CNS. qPCR found that separate treatment groups of DP and LA antioxidants under CHS resulted in significantly elevated levels of SEMA and DAPK (p-values: 0.008 and 0.033, respectively). SEMA is associated with aiding proper growth in POMC neurons, thus contributing to normal energy-related neuronal functioning. DAPK is associated with programmed cell death and tumor suppression. While the downregulation of DCX, GAN, and SPECC1L may compromise the hypothalamus, SEMA and DAPK seem to functionally be protective measures against the molecular impacts of CHS. Thus, using RNA-Seq we identified previously unstudied genes that appear to be implicated in the mediation of chronic heat stress in the hypothalamus tissue.